Transplantation of ex vivo expanded endothelial progenitor cells for therapeutic neovascularization

Endothelial precursor cell-based therapy to target the pathologic angiogenesis and compensate tumor hypoxia

Hypoxia-inducing pathologies as cancer develop pathologic and inefficient angiogenesis which rules tumor facilitating microenvironment, a key target for therapy. As such, the putative ability of endothelial precursor cells (EPCs) to specifically home to hypoxic sites of neovascularization prompted to design optimized, site-specific, cell-mediated, drug-/gene-targeting approach. Thus, EPC lines were established from aorta-gonad-mesonephros (AGM) of murine 10.5 dpc and 11.5 dpc embryo when endothelial repertoire is completed. Lines representing early endothelial differentiation steps were selected: MAgEC10.5 and MagEC11.5. Distinct in maturation, they differently express VEGF receptors, VE-cadherin and chemokine/receptors. MAgEC11.5, more differentiated than MAgEC 10.5, displayed faster angiogenesis in vitro, different response to hypoxia and chemokines. Both MAgEC lines cooperated to tube-like formation with mature endothelial cells and invaded tumor spheroids through a vasculogenesis-like process. In vivo, both MAgEC-formed vessels established blood flow. Intravenously injected, both MAgECs invaded Matrigel(TM)-plugs and targeted tumors. Here we show that EPCs (MAgEC11.5) target tumor angiogenesis and allow local overexpression of hypoxia-driven soluble VEGF-receptor2 enabling drastic tumor growth reduction. We propose that such EPCs, able to target tumor angiogenesis, could act as therapeutic gene vehicles to inhibit tumor growth by vessel normalization resulting from tumor hypoxia alleviation.

Endothelial progenitor cells as a biological marker of peripheral artery disease

The role of endothelial progenitor cells (EPCs) in peripheral artery disease (PAD) remains unclear. We hypothesized that EPC mobilization and function play a central role in the development of endothelial dysfunction and directly influence the degree of atherosclerotic burden in peripheral artery vessels. The number of circulating EPCs, defined as CD34(+)/KDR(+) cells, were assessed by flow cytometry in 91 subjects classified according to a predefined sample size of 31 non-diabetic PAD patients, 30 diabetic PAD patients, and 30 healthy volunteers. Both PAD groups had undergone endovascular treatment in the past. As a functional parameter, EPC colony-forming units were determined ex vivo. Apart from a broad laboratory analysis, a series of clinical measures using the ankle-brachial index (ABI), flow-mediated dilatation (FMD) and carotid intima-media thickness (cIMT) were investigated. A significant reduction of EPC counts and proliferation indices in both PAD groups compared to healthy subjects were observed. Low EPC number and pathological findings in the clinical assessment were strongly correlated to the group allocation. Multivariate statistical analysis revealed these findings to be independent predictors of disease appearance. Linear regression analysis showed the ABI to be a predictor of circulating EPC number (p=0.02). Moreover, the functionality of EPCs was correlated by linear regression (p=0.017) to cIMT. The influence of diabetes mellitus on EPCs in our study has to be considered marginal in already disease-affected patients. This study demonstrated that EPCs could predict the prevalence and severity of symptomatic PAD, with ABI as the determinant of the state of EPC populations in disease-affected groups.

Therapeutic effects of late outgrowth endothelial progenitor cells or mesenchymal stem cells derived from human umbilical cord blood on infarct repair

BACKGROUND

This study sought to systematically investigate the derivation of late outgrowth endothelial progenitor cells (late EPC) and mesenchymal stem cells (MSC) from umbilical cord blood (UCB) and to examine their therapeutic effects on myocardial infarction (MI).

METHODS

The expression of angiogenic genes was determined by qRT-PCR. Myocardial infarction (MI) was induced in rats, and cells were directly transplanted into the border regions of ischemic heart tissue.

RESULTS

Culture of UCB mononuclear cells yielded two distinct types of cells by morphology after 2 weeks in the same culture conditions. These cells were identified as late EPC and MSC, and each was intramyocardially injected into rat hearts after induction of MI. Echocardiography and histologic analyses demonstrated that both EPC and MSC improved cardiac function and enhanced vascularization, although fibrosis was reduced only in the EPC transplanted hearts. Different paracrine factors were enriched in EPC and MSC. However, once injected into the hearts, they induced similar types of paracrine factors in the heart. Transplanted EPC or MSC were mostly localized at the perivascular areas. This study demonstrated that EPC and MSC can be simultaneously derived from UCB under the same initial culture conditions, and that common paracrine factors are involved in the repair of MI.

CONCLUSION

Late EPC and MSC are effective for infarct repair, apparently mediated through common humoral mechanisms.

Injectable PLGA microspheres encapsulating WKYMVM peptide for neovascularization

Formyl peptide receptor-2 (FPR-2) is expressed in various cell types, such as phagocytes, fibroblasts, and endothelial cells. FPR-2 has been reported to play a significant role in inflammation and angiogenic response, and synthetic WKYMVm peptide has been identified as a novel peptide agonist for the FPR-2. In this study, we demonstrate that WKYMVm peptides stimulate the angiogenic potential of outgrowth endothelial cells (OECs). Upon WKYMVm peptide exposure, migration and proliferation of OECs were stimulated. WKYMVm effectively stimulated angiogenesis in tube formation assay and aortic ring assay. Furthermore, we fabricated injectable poly (lactide-co-glycolide) (PLGA) microspheres encapsulating WKYMVm peptides, which showed sustained release of cargo molecule. When WKYMVm peptide encapsulated microspheres were injected into the hind limb ischemia model, a single injection of microspheres was as effective as multiple injections of WKYMVm peptide in restoring blood flow from ischemic injury and promoting capillary growth. These results demonstrate that sustained release of WKYMVm peptide from microspheres in the application to ischemic hind limb extended angiogenic stimulation.

STATEMENT OF SIGNIFICANCE

Formyl peptide receptor (FPR) has been reported to play an important role in inflammation and angiogenic response. A synthetic WKYMVm peptide has been identified as a novel peptide activating the FPR-2 that is expressed in a various cell types, such as phagocytes, fibroblasts, and endothelial cells. In this manuscript we explored a unique property of high-affinity ligand for formyl peptide receptors-2 (FPR-2) (i.e., WKYMVm). WKYMVm-induced activation of FPR2 has been reported to be crucial in host defense and inflammation by activation of phagocytes, monocytes, and lymphocytes. In this study, highlight the efficacy of WKYMVm peptide's role in inducing neovascularization in vivo hind limb ischemia model when the peptide was released from injected PLGA microspheres in sustained manner. Our results demonstrate that sustained release of WKYMVm peptide from microspheres have extended angiogenic stimulation capacity.

Platelet density per monocyte predicts adverse events in patients after percutaneous coronary intervention

Monocyte recruitment to damaged endothelium is enhanced by platelet binding to monocytes and contributes to vascular repair. Therefore, we studied whether the number of platelets per monocyte affects the recurrence of adverse events in patients after percutaneous coronary intervention (PCI). Platelet-monocytes complexes with high and low median fluorescence intensities (MFI) of the platelet marker CD42b were isolated using cell sorting. Microscopic analysis revealed that a high platelet marker MFI on monocytes corresponded with a high platelet density per monocyte while a low platelet marker MFI corresponded with a low platelet density per monocyte (3.4 ± 0.7 vs 1.4 ± 0.1 platelets per monocyte, P=0.01). Using real-time video microscopy, we observed increased recruitment of high platelet density monocytes to endothelial cells as compared with low platelet density monocytes (P=0.01). Next, we classified PCI scheduled patients (N=263) into groups with high, medium and low platelet densities per monocyte and assessed the recurrence of adverse events. After multivariate adjustment for potential confounders, we observed a 2.5-fold reduction in the recurrence of adverse events in patients with a high platelet density per monocyte as compared with a low platelet density per monocyte [hazard ratio=0.4 (95% confidence interval, 0.2-0.8), P=0.01]. We show that a high platelet density per monocyte increases monocyte recruitment to endothelial cells and predicts a reduction in the recurrence of adverse events in patients after PCI. These findings may imply that a high platelet density per monocyte protects against recurrence of adverse events.

Proangiogenic cells enhanced persistent and physiologic neovascularization compared with macrophages

Proangiogenic cells (PACs) display surface markers and secrete angiogenic factors similar to those used by myelomonocytic cells, but, unlike myelomonocytic cells, PACs enhance neovascularization activity in experimental ischemic diseases. This study was performed to reveal the differential neovascularization activities of PACs compared with those of myelomonocytic cells. We cultured PACs and CD14(+)-derived macrophages (Macs) for 7 days. Most of the surface markers and cytokines in the two cell types were alike; the exceptions were KDR, β8 integrin, interleukin-8 and monocyte chemotactic protein-1. Unlike Macs, PACs significantly enhanced mesenchymal stem cell (MSC) transmigration. PACs and Macs increased neovascularization activity in an in vitro co-culture of human umbilical vein endothelial cells and MSCs and in an in vivo cotransplantation in Matrigel. However, the use of Macs resulted in inappropriately dilated and leaky vessels, whereas the use of PACs did not. We induced critical hindlimb ischemia in nude mice, and then transplanted PACs, Macs or vehicle into the mice. We obtained laser Doppler perfusion images weekly. At 2 weeks, mice treated with PACs showed significantly enhanced perfusion recovery in contrast to those treated with Macs. After day 7, when cells were depleted using a suicidal gene, viral thymidine kinase, to induce apoptosis of the cells in vivo by ganciclovir administration, we found that the improved perfusion was significantly abrogated in the PAC-treated group, whereas perfusion was not changed in the Mac-treated group. PACs caused an increase in healthy new vessels in in vitro and in vivo models of angiogenesis and enhanced long-term functional neovascularization activity in the hindlimb ischemia model, whereas Macs did not. Nevertheless, the angiogenic potential and long-term functional results for a specific cell type should be validated to confirm effectiveness and safety of the cell type for use in therapeutic angiogenesis procedures.

Enumeration and functional investigation of endothelial progenitor cells in neovascularization of diabetic foot ulcer rats with a Chinese 2-herb formula

BACKBROUND

We investigated the effect of a Chinese 2-herb formula (NF3) on the enumeration and angiogenic differentiation of endothelial progenitor cells (EPCs) in diabetic foot ulcer rats.

METHODS

EPCs and stromal cell-derived factor-1α (SDF-1α) were quantified by flow cytometry and ELISA, respectively. In vitro angiogenesis assays included proliferation, adhesion, migration and tube formation.

RESULTS

Our result demonstrated that NF3 (0.98 g/kg) could significantly enhance the circulating CD34(+) /VEGFR2(+) /CD45(-) EPCs levels in diabetic foot ulcer rats by 60% (P < 0.05) through the partial elevation of SDF-1α, restoring the mobilization ability of EPCs for wound neovascularization. We successfully isolated the BM-derived EPCs to study their angiogenic potential after NF3 treatment. BM-derived EPCs significantly expressed cell surface markers of CD34, CD146 and VEGFR2 (P < 0.05 - 0.01). NF3 could significantly stimulate the proliferation and attachment ability of EPCs dose-dependently (P < 0.01-0.001). Besides, NF3 could significantly augment EPCs migration (P < 0.001) and tube formation (P < 0.01-0.001).

CONCLUSIONS

NF3 modulated diabetic wound healing through regulation of systemic EPCs level and increase in local vascular formation.

Reprint of: Development of bioactive peptide amphiphiles for therapeutic cell delivery

There is great clinical interest in cell-based therapies for ischemic tissue repair in cardiovascular disease. However, the regenerative potential of these therapies is limited due to poor cell viability and minimal retention following application. We report here the development of bioactive peptide amphiphile nanofibers displaying the fibronectin-derived RGDS cell adhesion epitope as a scaffold for therapeutic delivery of bone marrow derived stem and progenitor cells. When grown on flat substrates, a binary peptide amphiphile system consisting of 10 wt.% RGDS-containing molecules and 90 wt.% negatively charged diluent molecules was found to promote optimal cell adhesion. This binary system enhanced adhesion 1.4-fold relative to substrates composed of only the non-bioactive diluent. Additionally, no enhancement was found upon scrambling the epitope and adhesion was no longer enhanced upon adding soluble RGDS to the cell media, indicating RGDS-specific adhesion. When encapsulated within self-assembled scaffolds of the binary RGDS nanofibers in vitro, cells were found to be viable and proliferative, increasing in number by 5.5 times after only 5 days, an effect again lost upon adding soluble RGDS. Cells encapsulated within a non-bioactive scaffold and those within a binary scaffold with scrambled epitope showed minimal viability and no proliferation. Cells encapsulated within this RGDS nanofiber gel also increase in endothelial character, evident by a decrease in the expression of CD34 paired with an increase in the expression of endothelial-specific markers VE-Cadherin, VEGFR2 and eNOS after 5days. In an in vivo study, nanofibers and luciferase-expressing cells were co-injected subcutaneously in a mouse model. The binary RGDS material supported these cells in vivo, evident by a 3.2-fold increase in bioluminescent signal attributable to viable cells; this suggests the material has an anti-apoptotic and/or proliferative effect on the transplanted bone marrow cells. We conclude that the binary RGDS-presenting nanofibers developed here demonstrate enhanced viability, proliferation and adhesion of associated bone marrow derived stem and progenitor cells. This study suggests potential for this material as a scaffold to overcome current limitations of stem cell therapies for ischemic diseases.

The role of FGF2 in migration and tubulogenesis of endothelial progenitor cells in relation to pro-angiogenic growth factor production

In recent years, special attention has been paid to finding new pro-angiogenic factors which could be used in gene therapy of vascular diseases such as critical limb ischaemia (CLI). Angiogenesis, the formation of new blood vessels, is a complex process dependent on different cytokines, matrix proteins, growth factors and other pro- or anti-angiogenic stimuli. Numerous lines of evidence suggest that key mediators of angiogenesis, vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) together with fibroblast growth factor2 (FGF2) are involved in regulation of the normal and pathological process of angiogenesis. However, less information is available on the complex interactions between these and other angiogenic factors. The aim of this study was to characterise the effect of fibroblast growth factor2 on biological properties of human endothelial progenitor cells with respect to the expression level of other regulatory cytokines. Ectopic expression of FGF2 in EP cells stimulates their pro-angiogenic behaviour, leading to increased proliferation, migration and tube formation abilities. Moreover, we show that the expression profile of VEGF and other pro-angiogenic cytokines, such as HGF, MCP2, and interleukins, is affected differently by FGF2 in EPC. In conclusion, we provide evidence that FGF2 directly affects not only the biological properties of EP cells but also the expression pattern and secretion of numerous chemocytokines. Our results suggest that FGF2 could be applied in therapeutic approaches for CLI and other ischaemic diseases of the vascular system in vivo.

MicroRNA-21 coordinates human multipotent cardiovascular progenitors therapeutic potential

Published clinical trials in patients with ischemic diseases show limited benefit of adult stem cell-based therapy, likely due to their restricted plasticity and commitment toward vascular cell lineage. We aim to uncover the potent regenerative ability of MesP1/stage-specific embryonic antigen 1 (SSEA-1)-expressing cardiovascular progenitors enriched from human embryonic stem cells (hESCs). Injection of only 10(4) hESC-derived SSEA-1(+) /MesP1(+) cells, or their progeny obtained after treatment with VEGF-A or PDGF-BB, was effective enough to enhance postischemic revascularization in immunodeficient mice with critical limb ischemia (CLI). However, the rate of incorporation of hESC-derived SSEA-1(+) /MesP1(+) cells and their derivatives in ischemic tissues was modest. Alternatively, these cells possessed a unique miR-21 signature that inhibited phosphotase and tensin homolog (PTEN) thereby activating HIF-1α and the systemic release of VEGF-A. Targeting miR-21 limited cell survival and inhibited their proangiogenic capacities both in the Matrigel model and in mice with CLI. We next assessed the impact of mR-21 in adult angiogenesis-promoting cells. We observed an impaired postischemic angiogenesis in miR-21-deficient mice. Notably, miR-21 was highly expressed in circulating and infiltrated monocytes where it targeted PTEN/HIF-1α/VEGF-A signaling and cell survival. As a result, miR-21-deficient mice displayed an impaired number of infiltrated monocytes and a defective angiogenic phenotype that could be partially restored by retransplantation of bone marrow-derived cells from wild-type littermates. hESC-derived SSEA-1(+) /MesP1(+) cells progenitor cells are powerful key integrators of therapeutic angiogenesis in ischemic milieu and miR-21 is instrumental in this process as well as in the orchestration of the biological activity of adult angiogenesis-promoting cells.

Brain-peripheral cell crosstalk in white matter damage and repair

White matter damage is an important part of cerebrovascular disease and may be a significant contributing factor in vascular mechanisms of cognitive dysfunction and dementia. It is well accepted that white matter homeostasis involves multifactorial interactions between all cells in the axon-glia-vascular unit. But more recently, it has been proposed that beyond cell-cell signaling within the brain per se, dynamic crosstalk between brain and systemic responses such as circulating immune cells and stem/progenitor cells may also be important. In this review, we explore the hypothesis that peripheral cells contribute to damage and repair after white matter damage. Depending on timing, phenotype and context, monocyte/macrophage can possess both detrimental and beneficial effects on oligodendrogenesis and white matter remodeling. Endothelial progenitor cells (EPCs) can be activated after CNS injury and the response may also influence white matter repair process. These emerging findings support the hypothesis that peripheral-derived cells can be both detrimental or beneficial in white matter pathology in cerebrovascular disease. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia, edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

Role of the microRNA, miR-206, and its target PIK3C2α in endothelial progenitor cell function – potential link with coronary artery disease

Coronary artery disease is a major cause of morbidity and mortality worldwide. Impaired endothelial function and integrity are major contributory factors to coronary artery disease. MicroRNAs have been proposed to play an important role in coronary artery disease pathogenesis. In the present study, the expression of miR-206 was found to be significantly upregulated in peripheral blood endothelial progenitor cells from patients with coronary artery disease compared to healthy donors. MiR-206 was found to regulate endothelial progenitor cell activities by targeting the protein kinase PIK3C2α, which showed decreased expression in coronary artery disease endothelial progenitor cells. Knockdown of miR-206 in coronary artery disease endothelial progenitor cells rescued their angiogenic and vasculogenic abilities both in vitro and in vivo in a mouse ischemic hindlimb model. Furthermore, knockdown of miR-206 activated not only PIK3C2α, but also the angiogenic signal modulators Akt and endothelial nitric oxide synthase. It is therefore proposed that repression of the phosphoinositide 3-kinase/Akt/endothelial nitric oxide synthase signal transduction pathway by miR-206 downregulates angiogenesis contributing to the pathophysiology of coronary artery disease.

Early outgrowth pro-angiogenic cell number and function do not correlate with left ventricular structure and function in conventional hemodialysis patients: a cross-sectional study

Background

Left ventricular hypertrophy (LVH) is commonly found in chronic dialysis (CD) recipients, and is associated with impaired microvascular cardiac perfusion and heart failure. In response to LVH and cardiac ischemia, early outgrowth pro-angiogenic cellS(EPCs) mobilize from the bone marrow to facilitate angiogenesis and endothelial repair. In the general population, EPC number and function correlate inversely with cardiovascular risk. In end-stage renal disease (ESRD), EPC number and function are generally reduced.

Objectives

To test whether left ventricular abnormalities retain their potent ability to promote EPC reparative responses in the setting of ESRD.

Design

Cross-sectional study.

Setting

St. Michael’s Hospital, Toronto, Ontario, Canada.

Patients

47 prevalent chronic dialysis recipients.

Measurements

(1) circulating CD34⁺ and CD133⁺ EPC number, (2) cultured EPC migratory ability, in vitro differentiation potential, and apoptosis rate, and (3) cardiac magnetic resonance-measured LV mass, volume and ejection fraction.

Methods

Bivariate correlation analysis was performed with Spearman's rho test.

Results

Of the 47 patients (mean age: 54 ± 13 years), the mean delivered urea reduction was 74 ± 10 %. Mean LV mass was 123 ± 38 g. Circulating CD34⁺ and CD133⁺ EPCs represented 0.14 % (IQR: 0.05 – 0.29 %) and 0.05 % (IQR: 0.01 – 0.10 %) of peripheral blood mononuclear cells. There were no significant correlations between any EPC parameter and measures of LV mass or ejection fraction.

Limitations

Lack of a non-ESRD control population, and the inability to measure all parameters of EPC function due to limitations in blood sampling. Our inability to measure cardiac VEGF expression prevented an assessment of changes in cardiac EPC mobilization signals.

Conclusions

These data suggest that in ESRD, the reparative EPC response to cardiac hypertrophy may be blunted. Further investigation of the effects of uremia on EPC physiology and its relationship to cardiac injury are required.

Hypoxia accelerates vascular repair of endothelial colony-forming cells on ischemic injury via STAT3-BCL3 axis

Introduction

Endothelial colony-forming cells (ECFCs) significantly improve tissue repair by providing regeneration potential within injured cardiovascular tissue. However, ECFC transplantation into ischemic tissue exhibits limited therapeutic efficacy due to poor engraftment in vivo. We established an adequate ex vivo expansion protocol and identified novel modulators that enhance functional bioactivities of ECFCs.

Methods

To augment the regenerative potential of ECFCs, functional bioactivities of hypoxia-preconditioned ECFCs (hypo-ECFCs) were examined.

Results

Phosphorylations of the JAK2/STAT3 pathway and clonogenic proliferation were enhanced by short-term ECFC culturing under hypoxia, whereas siRNA-targeting of STAT3 significantly reduced these activities. Expression of BCL3, a target molecule of STAT3, was increased in hypo-ECFCs. Moreover, siRNA inhibition of BCL3 markedly reduced survival of ECFCs during hypoxic stress in vitro and ischemic stress in vivo. In a hindlimb ischemia model of ischemia, hypo-ECFC transplantation enhanced blood flow ratio, capillary density, transplanted cell proliferation and survival, and angiogenic cytokine secretion at ischemic sites.

Conclusions

Hypoxia preconditioning facilitates functional bioactivities of ECFCs by mediating regulation of the STAT3-BCL3 axis. Thus, a hypoxic preconditioned ex vivo expansion protocol triggers expansion and functional bioactivities of ECFCs via modulation of the hypoxia-induced STAT3-BCL3 axis, suggesting that hypo-ECFCs offer a therapeutic strategy for accelerated neovasculogenesis in ischemic diseases.

Enhancing endothelial progenitor cell for clinical use

Circulating endothelial progenitor cells (EPCs) have been demonstrated to correlate negatively with vascular endothelial dysfunction and cardiovascular risk factors. However, translation of basic research into the clinical practice has been limited by the lack of unambiguous and consistent definitions of EPCs and reduced EPC cell number and function in subjects requiring them for clinical use. This article critically reviews the definition of EPCs based on commonly used protocols, their value as a biomarker of cardiovascular risk factor in subjects with cardiovascular disease, and strategies to enhance EPCs for treatment of ischemic diseases.

Endothelial NO-Synthase Gene-Enhanced Progenitor Cell Therapy for Pulmonary Arterial Hypertension: The PHACeT Trial

RATIONALE

Pulmonary arterial hypertension (PAH) remains a progressive and eventually lethal disease characterized by increased pulmonary vascular resistance because of loss of functional lung microvasculature, primarily at the distal (intracinar) arteriolar level. Cell-based therapies offer the potential to repair and regenerate the lung microcirculation and have shown promise in preclinical evaluation in experimental models of PAH.

OBJECTIVE

The Pulmonary Hypertension and Angiogenic Cell Therapy (PHACeT) trial was a phase 1, dose-escalating clinical study of the tolerability of culture-derived endothelial progenitor cells, transiently transfected with endothelial nitric oxide synthase, in patients with PAH refractory to PAH-specific therapies.

METHODS AND RESULTS

Seven to 50 million endothelial nitric oxide synthase-transfected endothelial progenitor cells, divided into 3 doses on consecutive days, were delivered into the right atrium via a multiport pulmonary artery catheter during continuous hemodynamic monitoring in an intensive care unit setting. Seven patients (5 women) received treatment from December 2006 to March 2010. Cell infusion was well tolerated, with no evidence of short-term hemodynamic deterioration; rather, there was a trend toward improvement in total pulmonary resistance during the 3-day delivery period. However, there was 1 serious adverse event (death) which occurred immediately after discharge in a patient with severe, end stage disease. Although there were no sustained hemodynamic improvements at 3 months, 6-minute walk distance was significantly increased at 1, 3, and 6 months.

CONCLUSION

Delivery of endothelial progenitor cells overexpressing endothelial nitric oxide synthase was tolerated hemodynamically in patients with PAH. Furthermore, there was evidence of short-term hemodynamic improvement, associated with long-term benefits in functional and quality of life assessments. However, future studies are needed to further establish the efficacy of this therapy.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00469027.

Isolation of Foreign Material-Free Endothelial Progenitor Cells Using CD31 Aptamer and Therapeutic Application for Ischemic Injury

Endothelial progenitor cells (EPCs) can be isolated from human bone marrow or peripheral blood and reportedly contribute to neovascularization. Aptamers are 40-120-mer nucleotides that bind to a specific target molecule, as antibodies do. To utilize apatmers for isolation of EPCs, in the present study, we successfully generated aptamers that recognize human CD31, an endothelial cell marker. CD31 aptamers bound to human umbilical cord blood-derived EPCs and showed specific interaction with human CD31, but not with mouse CD31. However, CD31 aptamers showed non-specific interaction with CD31-negative 293FT cells and addition of polyanionic competitor dextran sulfate eliminated non-specific interaction without affecting cell viability. From the mixture of EPCs and 293FT cells, CD31 aptamers successfully isolated EPCs with 97.6% purity and 94.2% yield, comparable to those from antibody isolation. In addition, isolated EPCs were decoupled from CD31 aptamers with a brief treatment of high concentration dextran sulfate. EPCs isolated with CD31 aptamers and subsequently decoupled from CD31 aptamers were functional and enhanced the restoration of blood flow when transplanted into a murine hindlimb ischemia model. In this study, we demonstrated isolation of foreign material-free EPCs, which can be utilized as a universal protocol in preparation of cells for therapeutic transplantation.

Superior Potential of CD34-Positive Cells Compared to Total Mononuclear Cells for Healing of Nonunion following Bone Fracture

We recently demonstrated that the local transplantation of human peripheral blood (PB) CD34+ cells, an endothelial/hematopoietic progenitor cell-rich population, contributes to fracture repair via vasculogenesis/angiogenesis and osteogenesis. Human PB mononuclear cells (MNCs) are also considered a potential cell fraction for neovascularization. We have previously shown the feasibility of human PB MNCs to enhance fracture healing. However, there is no report directly comparing the efficacy for fracture repair between CD34+ cells and MNCs. In addition, an unhealing fracture model, which does not accurately resemble a clinical setting, was used in our previous studies. To overcome these issues, we compared the capacity of human granulocyte colony-stimulating factor-mobilized PB (GM-PB) CD34+ cells and human GM-PB MNCs in a nonunion model, which more closely resembles a clinical setting. First, the effect of local transplantation of 1 × 105 GM-PB CD34+ cells (CD34+ group), 1 × 107 GM-PB MNCs (containing approximately 1 × 105 GM-PB CD34+ cells) (MNC group), and phosphate-buffered saline (PBS) (PBS group) on nonunion healing was compared. Similar augmentation of blood flow recovery at perinonunion sites was observed in the CD34+ and MNC groups. Meanwhile, a superior effect on nonunion repair was revealed by radiological, histological, and functional assessment in the CD34+ group compared with the other groups. Moreover, through in vivo and in vitro experiments, excessive inflammation induced by GM-PB MNCs was confirmed and believed to be one of the mechanisms underlying this potency difference. These results strongly suggest that local transplantation of GM-PB CD34+ cells is a practical and effective strategy for treatment of nonunion after fracture.

Strategies to Enhance the Efficiency of Endothelial Progenitor Cell Therapy by Ephrin B2 Pretreatment and Coadministration with Smooth Muscle Progenitor Cells on Vascular Function during the Wound-Healing Process in Irradiated or Nonirradiated Condition

Endothelial progenitor cell (EPC) transplantation has beneficial effects for therapeutic neovascularization. We therefore assessed the effect of a therapeutic strategy based on EPC administation in the healing of radiation-induced damage. To improve cell therapy for clinical use, we used pretreatment with ephrin B2-Fc (Eph-B2-Fc) and/or coadministration with smooth muscle progenitor cells. At day 3, EPCs promoted dermal wound healing in both nonirradiated and irradiated mice by 1.2- and 1.15-fold, respectively, compared with animals injected with phosphate-buffered saline. In addition, EPCs also improved skin-blood perfusion and capillary density in both irradiated and nonirradiated mice compared with PBS-injected animals. We also demonstrated that activation with Eph-B2-Fc increased wound closure by 1.6-fold compared with unstimulated EPCs in nonirradiated mice. Interestingly, the beneficial effect of Eph-B2-Fc was abolished in irradiated animals. In addition, we found that Eph-B2-Fc stimulation did not improve EPC-induced vascular permeability or adhesiveness compared to unstimulated EPCs. We hypothesized that this effect was due to high oxidative stress during irradiation, leading to inhibition of EPCs' beneficial effect on vascular function. In this line, we demonstated that, in irradiated conditions, N-acetyl-l-cysteine treatment restored the beneficial effect of EPC stimulation with Eph-B2-Fc in the wound healing process. In conclusion, stimulation by Eph-B2-Fc improved the beneficial effect of EPCs in physiological conditions and irradiated conditions only in association with antioxidant treatment. Additionally, cotherapy was beneficial in pathological conditions.

Characterization of Endothelial Progenitor Cell Interactions with Human Tropoelastin

The deployment of endovascular implants such as stents in the treatment of cardiovascular disease damages the vascular endothelium, increasing the risk of thrombosis and promoting neointimal hyperplasia. The rapid restoration of a functional endothelium is known to reduce these complications. Circulating endothelial progenitor cells (EPCs) are increasingly recognized as important contributors to device re-endothelialization. Extracellular matrix proteins prominent in the vessel wall may enhance EPC-directed re-endothelialization. We examined attachment, spreading and proliferation on recombinant human tropoelastin (rhTE) and investigated the mechanism and site of interaction. EPCs attached and spread on rhTE in a dose dependent manner, reaching a maximal level of 56±3% and 54±3%, respectively. EPC proliferation on rhTE was comparable to vitronectin, fibronectin and collagen. EDTA, but not heparan sulfate or lactose, reduced EPC attachment by 81±3%, while full attachment was recovered after add-back of manganese, inferring a classical integrin-mediated interaction. Integrin αVβ3 blocking antibodies decreased EPC adhesion and spreading on rhTE by 39±3% and 56±10% respectively, demonstrating a large contribution from this specific integrin. Attachment of EPCs on N-terminal rhTE constructs N25 and N18 accounted for most of this interaction, accompanied by comparable spreading. In contrast, attachment and spreading on N10 was negligible. αVβ3 blocking antibodies reduced EPC spreading on both N25 and N18 by 45±4% and 42±14%, respectively. In conclusion, rhTE supports EPC binding via an integrin mechanism involving αVβ3. N25 and N18, but not N10 constructs of rhTE contribute to EPC binding. The regulation of EPC activity by rhTE may have implications for modulation of the vascular biocompatibility of endovascular implants.

Acidic Fibroblast Growth Factor Promotes Endothelial Progenitor Cells Function via Akt/FOXO3a Pathway

Acidic fibroblast growth factor (FGF1) has been suggested to enhance the functional activities of endothelial progenitor cells (EPCs). The Forkhead homeobox type O transcription factors (FOXOs), a key substrate of the survival kinase Akt, play important roles in regulation of various cellular processes. We previously have shown that FOXO3a is the main subtype of FOXOs expressed in EPCs. Here, we aim to determine whether FGF1 promotes EPC function through Akt/FOXO3a pathway. Human peripheral blood derived EPCs were transduced with adenoviral vectors either expressing a non-phosphorylable, constitutively active triple mutant of FOXO3a (Ad-TM-FOXO3a) or a GFP control (Ad-GFP). FGF1 treatment improved functional activities of Ad-GFP transduced EPCs, including cell viability, proliferation, antiapoptosis, migration and tube formation, whereas these beneficial effects disappeared by Akt inhibitor pretreatment. Moreover, EPC function was declined by Ad-TM-FOXO3a transduction and failed to be attenuated even with FGF1 treatment. FGF1 upregulated phosphorylation levels of Akt and FOXO3a in Ad-GFP transduced EPCs, which were repressed by Akt inhibitor pretreatment. However, FGF1 failed to recover Ad-TM-FOXO3a transduced EPCs from dysfunction. These data indicate that FGF1 promoting EPC function is at least in part mediated through Akt/FOXO3a pathway. Our study may provide novel ideas for enhancing EPC angiogenic ability and optimizing EPC transplantation therapy in the future.

Increased endothelial progenitor cell circulation and VEGF production in a rat model of noise-induced hearing loss

CONCLUSIONS

The vascular endothelial growth factor (VEGF)-mediated mechanism of endothelial progenitor cell (EPC) mobilization, migration, and differentiation may occur in response to noise-induced acoustic trauma of the cochlea, leading to the protection of cochlear function.

OBJECTIVE

The purpose of this study was to analyze changes in the cochlear vessel under an intensive noise environment.

METHODS

Sixty male Sprague-Dawley rats were randomly divided into six groups. Acoustic trauma was induced by 120 dB SPL white noise for 4 h. Auditory function was evaluated by the auditory brainstem response threshold. Morphological changes of the cochleae, the expression of VEGF, and the circulation of EPCs in the peripheral blood were studied by immunohistochemistry, Western blotting analysis, scanning electron microscopy, and flow cytometry.

RESULTS

Vascular recovery of the cochlea began after noise exposure. The change in the number of EPCs was consistent with the expression of VEGF at different time points after noise exposure. We propose that VEGF evokes specific permeable and chemotactic effects on the vascular endothelial cells. These effects can mobilize EPCs into the peripheral blood, leading the EPCs to target damaged sites and to exert a neoangiogenic effect.

Reprogramming of myeloid angiogenic cells by Bartonella henselae leads to microenvironmental regulation of pathological angiogenesis

The contribution of myeloid cells to tumour microenvironments is a decisive factor in cancer progression. Tumour-associated macrophages (TAMs) mediate tumour invasion and angiogenesis through matrix remodelling, immune modulation and release of pro-angiogenic cytokines. Nothing is known about how pathogenic bacteria affect myeloid cells in these processes. Here we show that Bartonella henselae, a bacterial pathogen causing vasculoproliferative diseases (bacillary angiomatosis), reprogrammes human myeloid angiogenic cells (MACs), a pro-angiogenic subset of circulating progenitor cells, towards a TAM-like phenotype with increased pro-angiogenic capacity. B. henselae infection resulted in inhibition of cell death, activation of angiogenic cellular programmes and induction of M2 macrophage polarization. MACs infected with B. henselae incorporated into endothelial sprouts and increased angiogenic growth. Infected MACs developed a vascular mimicry phenotype in vitro, and expression of B. henselae adhesin A was essential in inducing these angiogenic effects. Secretome analysis revealed that increased pro-angiogenic activities were associated with the creation of a tumour-like microenvironment dominated by angiogenic inflammatory cytokines and matrix remodelling compounds. Our results demonstrate that manipulation of myeloid cells by pathogenic bacteria can contribute to microenvironmental regulation of pathological tissue growth and suggest parallels underlying both bacterial infections and cancer.

Transplanted Peripheral Blood Stem Cells Mobilized by Granulocyte Colony-Stimulating Factor Promoted Hindlimb Functional Recovery After Spinal Cord Injury in Mice

Granulocyte colony-stimulating factor (G-CSF) mobilizes peripheral blood stem cells (PBSCs) derived from bone marrow. We hypothesized that intraspinal transplantation of PBSCs mobilized by G-CSF could promote functional recovery after spinal cord injury. Spinal cords of adult nonobese diabetes/severe immunodeficiency mice were injured using an Infinite Horizon impactor (60 kdyn). One week after the injury, 3.0 µl of G-CSF-mobilized human mononuclear cells (MNCs; 0.5 × 10(5)/µl), G-CSF-mobilized human CD34-positive PBSCs (CD34; 0.5 × 10(5)/µl), or normal saline was injected to the lesion epicenter. We performed immunohistochemistry. Locomotor recovery was assessed by Basso Mouse Scale. The number of transplanted human cells decreased according to the time course. The CD31-positive area was significantly larger in the MNC and CD34 groups compared with the vehicle group. The number of serotonin-positive fibers was significantly larger in the MNC and CD34 groups than in the vehicle group. Immunohistochemistry revealed that the number of apoptotic oligodendrocytes was significantly smaller in cell-transplanted groups, and the areas of demyelination in the MNC- and CD34-transplanted mice were smaller than that in the vehicle group, indicating that cell transplantation suppressed oligodendrocyte apoptosis and demyelination. Both the MNC and CD34 groups showed significantly better hindlimb functional recovery compared with the vehicle group. There was no significant difference between the two types of transplanted cells. Intraspinal transplantation of G-CSF-mobilized MNCs or CD34-positive cells promoted angiogenesis, serotonergic fiber regeneration/sparing, and preservation of myelin, resulting in improved hindlimb function after spinal cord injury in comparison with vehicle-treated control mice. Transplantation of G-CSF-mobilized PBSCs has advantages for treatment of spinal cord injury in the ethical and immunological viewpoints, although further exploration is needed to move forward to clinical application.

Endothelial progenitor cells inhibit platelet function in a P-selectin-dependent manner

Background

The role of endothelial progenitor cells (EPCs) in vascular repair is related to their recruitment at the sites of injury and their interaction with different components of the circulatory system. We have previously shown that EPCs bind and inhibit platelet function and impair thrombus formation via prostacyclin secretion, but the role of EPC binding to platelet P-selectin in this process has not been fully characterized. In the present study, we assessed the impact of EPCs on thrombus formation and we addressed the implication of P-selectin in this process.

Methods

EPCs were generated from human peripheral blood mononuclear cells cultured on fibronectin in conditioned media. The impact of EPCs on platelet aggregation and thrombus formation was investigated in P-selectin deficient (P-sel^−/−) mice and their wild-type (WT) counterparts.

Results

EPCs significantly and dose-dependently impaired collagen-induced whole blood platelet aggregation in WT mice, whereas no effects were observed in P-sel^−/− mice. Moreover, in a ferric chloride-induced arterial thrombosis model, infusion of EPCs significantly reduced thrombus formation in WT, but not in P-sel^−/− mice. Furthermore, the relative mass of thrombi generated in EPC-treated P-sel^−/− mice were significantly larger than those in EPC-treated WT mice, and the number of EPCs recruited within the thrombi and along the arterial wall was reduced in P-sel^−/− mice as compared to WT mice.

Conclusion

This study shows that EPCs impair platelet aggregation and reduce thrombus formation via a cellular mechanism involving binding to platelet P-selectin. These findings add new insights into the role of EPC-platelet interactions in the regulation of thrombotic events during vascular repair.

The Secretome of Hydrogel-Coembedded Endothelial Progenitor Cells and Mesenchymal Stem Cells Instructs Macrophage Polarization in Endotoxemia

: We previously reported the delivery of endothelial progenitor cells (EPCs) embedded in hyaluronic acid-based (HA)-hydrogels protects renal function during acute kidney injury (AKI) and promotes angiogenesis. We attempted to further ameliorate renal dysfunction by coembedding EPCs with renal mesenchymal stem cells (MSCs), while examining their paracrine influence on cytokine/chemokine release and proinflammatory macrophages. A live/dead assay determined whether EPC-MSC coculturing improved viability during lipopolysaccharide (LPS) treatment, and HA-hydrogel-embedded delivery of cells to LPS-induced AKI mice was assessed for effects on mean arterial pressure (MAP), renal blood flow (RBF), circulating cytokines/chemokines, serum creatinine, proteinuria, and angiogenesis (femoral ligation). Cytokine/chemokine release from embedded stem cells was examined, including effects on macrophage polarization and release of proinflammatory molecules. EPC-MSC coculturing improved stem cell viability during LPS exposure, an effect augmented by MSC hypoxic preconditioning. The delivery of coembedded EPCs with hypoxic preconditioned MSCs to AKI mice demonstrated additive improvement (compared with EPC delivery alone) in medullary RBF and proteinuria, with comparable effects on serum creatinine, MAP, and angiogenesis. Exposure of proinflammatory M1 macrophages to EPC-MSC conditioned medium changed their polarization to anti-inflammatory M2. Incubation of coembedded EPCs-MSCs with macrophages altered their release of cytokines/chemokines, including enhanced release of anti-inflammatory interleukin (IL)-4 and IL-10. EPC-MSC delivery to endotoxemic mice elevated the levels of circulating M2 macrophages and reduced the circulating cytokines/chemokines. In conclusion, coembedding EPCs-MSCs improved their resistance to stress, impelled macrophage polarization from M1 to M2 while altering their cytokine/chemokines release, reduced circulating cytokines/chemokines, and improved renal and vascular function when MSCs were hypoxically preconditioned.

SIGNIFICANCE

This report provides insight into a new therapeutic approach for treatment of sepsis and provides a new and improved strategy using hydrogels for the delivery of stem cells to treat sepsis and, potentially, other injuries and/or diseases. The delivery of two different stem cell lines (endothelial progenitor cells and mesenchymal stem cells; delivered alone and together) embedded in a protective bioengineered scaffolding (hydrogel) offers many therapeutic benefits for the treatment of sepsis. This study shows how hydrogel-delivered stem cells elicit their effects and how hydrogel embedding enhances the therapeutic efficacy of delivered stem cells. Hydrogel-delivered stem cells influence the components of the overactive immune system during sepsis and work to counterbalance the release of many proinflammatory and prodamage substances from immune cells, thereby improving the associated vascular and kidney damage.

Efficient gene disruption in cultured primary human endothelial cells by CRISPR/Cas9

RATIONALE

The participation of endothelial cells (EC) in many physiological and pathological processes is widely modeled using human EC cultures, but genetic manipulation of these untransformed cells has been technically challenging. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 nuclease (Cas9) technology offers a promising new approach. However, mutagenized cultured cells require cloning to yield homogeneous populations, and the limited replicative lifespan of well-differentiated human EC presents a barrier for doing so.

OBJECTIVE

To create a simple but highly efficient method using CRISPR/Cas9 to generate biallelic gene disruption in untransformed human EC.

METHODS AND RESULTS

To demonstrate proof-of-principle, we used CRISPR/Cas9 to disrupt the gene for the class II transactivator. We used endothelial colony forming cell-derived EC and lentiviral vectors to deliver CRISPR/Cas9 elements to ablate EC expression of class II major histocompatibility complex molecules and with it, the capacity to activate allogeneic CD4(+) T cells. We show the observed loss-of-function arises from biallelic gene disruption in class II transactivator that leaves other essential properties of the cells intact, including self-assembly into blood vessels in vivo, and that the altered phenotype can be rescued by reintroduction of class II transactivator expression.

CONCLUSIONS

CRISPR/Cas9-modified human EC provides a powerful platform for vascular research and for regenerative medicine/tissue engineering.

Modulating the vascular response to limb ischemia: angiogenic and cell therapies

The age-adjusted prevalence of peripheral arterial disease in the US population has been estimated to approach 12%. The clinical consequences of occlusive peripheral arterial disease include pain on walking (claudication), pain at rest, and loss of tissue integrity in the distal limbs; the latter may ultimately lead to amputation of a portion of the lower extremity. Surgical bypass techniques and percutaneous catheter-based interventions may successfully reperfuse the limbs of certain patients with peripheral arterial disease. In many patients, however, the anatomic extent and distribution of arterial occlusion is too severe to permit relief of pain and healing of ischemic ulcers. No effective medical therapy is available for the treatment of such patients, for many of whom amputation represents the only hope for alleviation of symptoms. The ultimate failure of medical treatment and procedural revascularization in significant numbers of patients has led to attempts to develop alternative therapies for ischemic disease. These strategies include administration of angiogenic cytokines, either as recombinant protein or as gene therapy, and more recently, to investigations of stem/progenitor cell therapy. The purpose of this review is to provide an outline of the preclinical basis for angiogenic and stem cell therapies, review the clinical research that has been done, summarize the lessons learned, identify gaps in knowledge, and suggest a course toward successfully addressing an unmet medical need in a large and growing patient population.

Icariin promotes angiogenic differentiation and prevents oxidative stress-induced autophagy in endothelial progenitor cells

Reduced tissue levels of endothelial progenitor cells (EPCs) and functional impairment of endothelium are frequently observed in patients with diabetes and cardiovascular disease. The vascular endothelium is specifically sensitive to oxidative stress, and this is one of the mechanisms that causes widespread endothelial dysfunction in most cardiovascular diseases and disorders. Hence attention has increasingly been paid to enhance mobilization and differentiation of EPCs for therapeutic purposes. The aim of this study was to investigate whether Icariin, a natural bioactive component known from traditional Chinese Medicine, can induce angiogenic differentiation and inhibit oxidative stress-induced cell dysfunction in bone marrow-derived EPCs (BM-EPCs), and, if so, through what mechanisms. We observed that treatment of BM-EPCs with Icariin significantly promoted cell migration and capillary tube formation, substantially abrogated hydrogen peroxide (H2 O2 )-induced apoptotic and autophagic programmed cell death that was linked to the reduced intracellular reactive oxygen species levels and restored mitochondrial membrane potential. Icariin downregulated endothelial nitric oxide synthase 3, as well as nicotinamide-adenine dinucleotide phosphate-oxidase expression upon H2 O2 induction. These antiapoptotic and antiautophagic effects of Icariin are possibly mediated by restoring the loss of mammalian target of rapamycin /p70S6K/4EBP1 phosphorylation as well as attenuation of ATF2 and ERK1/2 protein levels after H2 O2 treatment. In summary, favorable modulation of the angiogenesis and redox states in BM-EPCs make Icariin a promising proangiogenic agent both enhancing vasculogenesis and protecting against endothelial dysfunction.

Interleukin-3 greatly expands non-adherent endothelial forming cells with pro-angiogenic properties

Circulating endothelial progenitor cells (EPCs) provide revascularisation for cardiovascular disease and the expansion of these cells opens up the possibility of their use as a cell therapy. Herein we show that interleukin-3 (IL3) strongly expands a population of human non-adherent endothelial forming cells (EXnaEFCs) with low immunogenicity as well as pro-angiogenic capabilities in vivo, making their therapeutic utilisation a realistic option. Non-adherent CD133(+) EFCs isolated from human umbilical cord blood and cultured under different conditions were maximally expanded by day 12 in the presence of IL3 at which time a 350-fold increase in cell number was obtained. Cell surface marker phenotyping confirmed expression of the hematopoietic progenitor cell markers CD133, CD117 and CD34, vascular cell markers VEGFR2 and CD31, dim expression of CD45 and absence of myeloid markers CD14 and CD11b. Functional experiments revealed that EXnaEFCs exhibited classical properties of endothelial cells (ECs), namely binding of Ulex europaeus lectin, up-take of acetylated-low density lipoprotein and contribution to EC tube formation in vitro. These EXnaEFCs demonstrated a pro-angiogenic phenotype within two independent in vivo rodent models. Firstly, a Matrigel plug assay showed increased vascularisation in mice. Secondly, a rat model of acute myocardial infarction demonstrated reduced heart damage as determined by lower levels of serum creatinine and a modest increase in heart functionality. Taken together, these studies show IL3 as a potent growth factor for human CD133(+) cell expansion with clear pro-angiogenic properties (in vitro and in vivo) and thus may provide clinical utility for humans in the future.

Hyperhomocysteinemia suppresses bone marrow CD34+/VEGF receptor 2+ cells and inhibits progenitor cell mobilization and homing to injured vasculature-a role of β1-integrin in progenitor cell migration and adhesion

Hyperhomocysteinemia (HHcy) impairs re-endothelialization and accelerates vascular remodeling. The role of CD34(+)/VEGF receptor (VEGFR) 2(+) progenitor cells (PCs) in vascular repair in HHcy is unknown. We studied the effect of HHcy on PCs and its role in vascular repair in severe HHcy (∼150 μM), which was induced in cystathionine-β synthase heterozygous mice fed a high-methionine diet for 8 weeks. Vascular injury was introduced by carotid air-dry endothelium denudation. CD34(+)/VEGFR2(+) cells were examined by flow cytometry. HHcy reduced bone marrow (BM) CD34(+)/VEGFR2(+) cells and suppressed replenishment of postinjury CD34(+)/VEGFR2(+) cells in peripheral blood (PB). Donor green fluorescent protein-positive PC homing to the injured vessel was reduced in HHcy after CD34(+) PCs from enhanced green fluorescent protein mice were adoptively transferred following carotid injury. CD34(+) PC transfusion partially reversed HHcy-suppressed re-endothelialization and HHcy-induced neointimal formation. Furthermore, homocysteine (Hcy) inhibited proliferation, adhesion, and migration and suppressed β1-integrin expression and activity in human CD34(+) endothelial colony-forming cells (ECFCs) isolated from PBs in a dose-dependent manner. A functional-activating β1-integrin antibody rescued Hcy-suppressed adhesion and migration in CD34(+) ECFCs. In conclusion, HHcy reduces BM CD34(+)/VEGFR2(+) generation and suppresses CD34(+)/VEGFR2(+) cell mobilization and homing to the injured vessel via β1-integrin inhibition, which partially contributes to impaired re-endothelialization and vascular remodeling.

Use of nanoparticles to monitor human mesenchymal stem cells transplanted into penile cavernosum of rats with erectile dysfunction

Purpose

This study was performed to examine the treatment of erectile dysfunction by use of superparamagnetic iron oxide nanoparticles-labeled human mesenchymal stem cells (SPION-MSCs) transplanted into the cavernous nerve injured cavernosa of rats as monitored by molecular magnetic resonance imaging (MRI).

Materials and Methods

Eight-week-old male Sprague-Dawley rats were divided into three groups of 10 rats each: group 1, sham operation; group 2, cavernous nerve injury; group 3, SPION-MSC treatment after cavernous nerve injury. Immediately after the cavernous nerve injury in group 3, SPION-MSCs were injected into the cavernous nerve injured cavernosa. Serial T2-weighted MRI was done immediately after injection and at 2 and 4 weeks. Erectile response was assessed by cavernous nerve stimulation at 2 and 4 weeks.

Results

Prussian blue staining of SPION-MSCs revealed abundant uptake of SPION in the cytoplasm. After injection of 1×10⁶ SPION-MSCs into the cavernosa of rats, T2-weighted MRI showed a clear hypointense signal induced by the injection. The presence of SPION in the corpora cavernosa was confirmed with Prussian blue staining. At 2 and 4 weeks, rats with cavernous nerve injury had significantly lower erectile function than did rats without cavernous nerve injury (p<0.05). The group transplanted with SPION-MSCs showed higher erectile function than did the group without SPION-MSCs (p<0.05). The presence of SPION-MSCs for up to 4 weeks was confirmed by MRI imaging and Prussian blue staining in the corpus cavernosa.

Conclusions

Transplanted SPION-MSCs existed for up to 4 weeks in the cavernous nerve injured cavernosa of rats. Erectile dysfunction recovered and could be monitored by MRI.

C-reactive protein genetic variant is associated with diabetic retinopathy in Chinese patients with type 2 diabetes

BACKGROUND

Diabetic retinopathy (DR) is an important microvascular complication of diabetes with a high concordance rate in patients with diabetes. Inflammation is supposed to participate in the development of DR. This study aimed to investigate whether genetic variants of CRP are associated with DR.

METHODS

A total of 1,018 patients with type 2 diabetes were recruited in this study. Of these patients, 618 were diagnosed with DR, 400 were patients with diabetes for over 10 years but without DR, considered as cases and controls for DR, respectively. Four tagging SNPs (rs2808629, rs3093077, rs1130864 and rs2808634) within CRP region were genotyped for all the participants. Fundus photography was performed for diagnosis and classification for DR.

RESULTS

rs2808629 was significantly associated with increased susceptibility to DR (odds ratio 1.296, 95% CI 1.076-1.561, P = 0.006, empirical P = 0.029, for G allele). This association remained significant after adjustment for confounding factors (odds ratio 1.261, 95% CI 1.022-1.555, P = 0.030).

CONCLUSIONS

In this study, we found CRP rs2808629 was associated with DR in the Chinese patients with type 2 diabetes.

A critical role of CXCR2 PDZ-mediated interactions in endothelial progenitor cell homing and angiogenesis

Bone marrow-derived endothelial progenitor cells (EPCs) contribute to neovessel formation in response to growth factors, cytokines, and chemokines. Chemokine receptor CXCR2 and its cognate ligands are reported to mediate EPC recruitment and angiogenesis. CXCR2 possesses a consensus PSD-95/DlgA/ZO-1 (PDZ) motif which has been reported to modulate cellular signaling and functions. Here we examined the potential role of the PDZ motif in CXCR2-mediated EPC motility and angiogenesis. We observed that exogenous CXCR2 C-tail significantly inhibited in vitro EPC migratory responses and angiogenic activities, as well as in vivo EPC angiogenesis. However, the CXCR2 C-tail that lacks the PDZ motif (ΔTTL) did not cause any significant changes of these functions in EPCs. In addition, using biochemical assays, we demonstrated that the PDZ scaffold protein NHERF1 specifically interacted with CXCR2 and its downstream effector, PLC-β3, in EPCs. This suggests that NHERF1 might cluster CXCR2 and its relevant signaling molecules into a macromolecular signaling complex modulating EPC cellular functions. Taken together, our data revealed a critical role of a PDZ-based CXCR2 macromolecular complex in EPC homing and angiogenesis, suggesting that targeting this complex might be a novel and effective strategy to treat angiogenesis-dependent diseases.

Age-dependent healing potential of anterior cruciate ligament remnant-derived cells

BACKGROUND

The anterior cruciate ligament (ACL) does not heal spontaneously after injury, and ACL patients of different ages respond differently to treatment. Although ACL-derived CD34-positive cells contribute to bone-tendon healing after ACL reconstruction, the relationship between the healing potential of ACL-derived cells and a patient's age is unknown.

HYPOTHESIS

ACL-derived cells from young patients will have a greater effect on the maturation of bone-tendon integration in an immunodeficient rat model of ACL reconstruction compared with cells derived from older patients.

STUDY DESIGN

Controlled laboratory study.

METHODS

Sixty 10-week-old female immunodeficient rats underwent ACL reconstruction (using the autologous flexor digitorum longus tendon as a graft) followed by intracapsular administration of ACL-derived cells from patients aged 10 to 19 years (younger group) or patients aged 30 to 39 years (older group), or they were given phosphate-buffered saline (PBS; PBS group). Histologic, radiographic, and biomechanical examinations were performed 2 to 8 weeks after surgery. In addition, intrinsic and human cell-derived angiogenesis and osteogenesis were examined by immunohistochemistry.

RESULTS

In the younger group, histologic assessment demonstrated early bone-tendon healing, which induced endochondral ossification-like integration. Micro-computed tomography showed a statistically significant reduction in the area of tibial bone tunnel in the younger group (week 4, 20.0% ± 11.2% reduction; week 8, 25.7% ± 5.6% reduction) compared with the older group (week 4, 1.8% ± 3.0% reduction; week 8, 4.0% ± 5.9% reduction) and the PBS group (week 4, -0.5% ± 3.2% reduction; week 8, 3.3% ± 5.2% reduction) (week 4, P < .05; week 8, P < .01). Failure loads during tensile testing demonstrated a significantly higher ultimate load to failure in the younger group (17.52 ± 4.01 N) compared with the older (8.05 ± 2.91 N) and PBS (7.01 ± 3.16 N) groups (P < .05), and isolectin B4 and rat osteocalcin immunostaining indicated enhanced intrinsic angiogenesis and osteogenesis in the younger group. There was no statistically significant difference in the results of radiographic and biomechanical examinations between the older and PBS groups. Double immunohistochemistry for human-specific endothelial cell and osteoblast markers demonstrated a greater ability of differentiation into endothelial cells and osteoblasts in the younger group.

CONCLUSION

ACL-derived cells from younger patients enhanced early bone-tendon healing in an immunodeficient rat model of ACL reconstruction.

CLINICAL RELEVANCE

Surgeons should consider a patient's age when performing ACL reconstruction with remnant preservation or ruptured tissue incorporation, as this can predict healing ability.

PAR1-stimulated platelet releasate promotes angiogenic activities of endothelial progenitor cells more potently than PAR4-stimulated platelet releasate

BACKGROUND

Endothelial progenitor cells (EPCs) are important for endothelial regeneration and angiogenesis. Thrombin protease-activated receptor 1 (PAR1) PAR1 and PAR4 stimulation induces selective release of platelet proangiogenic and antiangiogenic regulators.

OBJECTIVE

To investigate if PAR1-stimulated platelet releasate (PAR1-PR) and PAR4-PR regulate angiogenic properties of EPCs in different manners.

METHODS AND RESULTS

EPCs were generated from peripheral mononuclear cell culture. Washed platelets (2 × 10(9) mL(-1)) were stimulated by PAR1-activating peptide (PAR1-AP; 10 μmol L(-1)) or PAR4-AP (100 μmol L(-1)) to prepare PAR1-PR and PAR4-PR, respectively. PAR1-PR or PAR4-PR had little influence on EPC proliferation. EPC migration experiments using a modified Boyden chamber showed that both platelet releasates facilitated EPC migration. As for in vitro tube formation on Matrigel, PAR1-PR and PAR4-PR similarly enhanced capillary-like network formation of EPCs in the complete EPC medium containing 10% FBS and a cocktail of growth factors, while PAR1-PR more profoundly increased EPC tube formation in basal culture medium supplemented with only 0.5% FBS than did PAR4-PR. The latter was confirmed in the murine angiogenesis model of subcutaneous Matrigel implantation. Moreover, blockade of vascular endothelial growth factor, stromal cell-derived factor 1α, or matrix metalloproteinases attenuated EPC migration and tube formation, suggesting a cooperation of these factors in the enhancements.

CONCLUSIONS

PAR1-PR enhances vasculogenesis more potently than PAR4-PR, and the enhancements require a cooperation of multiple platelet-derived angiogenic regulators.

A novel peritoneum derived vascular prosthesis formed on a latex catheter in an SDF-1 chemokine enriched environment: a pilot study

INTRODUCTION

Although saphenous vein grafts are widely used conduits for coronary artery bypass graft surgery, their clinical value remains limited due to high failure rates. The aim of the study was to evaluate feasibility, safety, and biocompatibility of peritoneal derived vascular grafts (PDVG) formed on a silicone-coated, latex, Foley catheter in a stromal cell-derived factor (SDF-1)- enriched environment.

METHODS

Foley catheters were implanted into the parietal wall of 8 sheep. After 21 days the peritoneal cavity was re-opened and the newly formed tissue fragments were harvested. The animals were randomly assigned into: (1) study group in which conduits were incubated in a solution containing SDF-1, (2) control group without SDF-1 incubation. Left carotid arteries were accessed and "end-to-side" anastomoses were performed. Biological materials for histological examination were taken at 4, 7, 10, and 14 days.

RESULTS AND CONCLUSIONS

The study proved safety, feasibility, and biocompatibility of PDVG formed on the basis of a silicone-coated, latex catheter in an SDF-1 chemokine-enriched environment. These biological grafts effectively integrated with the native high-pressure arterial environment in an ovine model and provided favorable vascular profile. The potential clinical value of this technology needs to be further elucidated in long-term preclinical and clinical studies.

Circulating mesenchymal stem cells in patients with hypertrophic cardiomyopathy

BACKGROUND

This study examines the mobilization of mesenchymal stem cells (MSCs) in patients with hypertrophic cardiomyopathy (HCM) compared to healthy individuals. The pathogenesis of myocardial hypertrophy in HCM is not fully understood. MSCs are involved in the process of neovascularization, fibrosis, and ventricular wall remodeling.

METHODS AND RESULTS

We included 40 patients with HCM and 23 healthy individuals. Using flow cytometry, we measured MSCs in peripheral blood, as a population of CD45-/CD34-/CD90+ cells and also as a population of CD45-/CD34-/CD105+ cells. The resulting MSC counts were expressed as percentages of the total cells. Patients with HCM were found to have a greater percentage of circulating CD45-/CD34-CD34-/CD90+ cells compared to controls (0.0041±0.005% vs. 0.0007±0.001%, respectively, P<.001). No significant difference in circulating CD45-/CD34-/CD105+ cells in the peripheral blood was found between HCM patients and controls (0.016±0.018% vs. 0.012±0.014%, respectively, P=.4). Notably, circulating CD45-/CD34-/CD90+ cells were positively correlated with left ventricular mass index (r=0.54, P<.001).

CONCLUSIONS

Patients with HCM reveal an increased mobilization of MSCs compared to healthy individuals. Although further research is needed to reveal the clinical significance of our findings, our data open a new dimension in the pathophysiology of the disease and may indicate new future therapeutic possibilities.

CD144, CD146 and VEGFR-2 properly identify circulating endothelial cell

Studies evaluating circulating endothelial cells by flow cytometry are faced by a lack of consensus about the best combination of monoclonal antibodies to be used. The rarity of these cells in peripheral blood, which represent 0.01% of mononuclear cells, drastically increases this challenge.

Objective

The aim of this study is to suggest some combinations of markers that would safely and properly identify these cells.

Methods

Flow cytometry analysis of circulating endothelial cells was performed applying three different panels composed of different combinations of the CD144, CD146, CD31, CD133, CD45 and anti-Vascular endothelial growth factor receptor-2 antibodies.

Results

In spite of the rarity of the events, they were detectable and presented similar inter-person numbers of circulating endothelial cells.

Conclusion

The combination of markers successfully identified the circulating endothelial cells in healthy individuals, with the use of three different panels confirming the obtained data as reliable.

Direct intracardiac injection of umbilical cord-derived stromal cells and umbilical cord blood-derived endothelial cells for the treatment of ischemic cardiomyopathy

The development of new therapeutic strategies is necessary to reduce the worldwide social and economic impact of cardiovascular disease, which produces high rates of morbidity and mortality. A therapeutic option that has emerged in the last decade is cell therapy. The aim of this study was to compare the effect of transplanting human umbilical cord-derived stromal cells (UCSCs), human umbilical cord blood-derived endothelial cells (UCBECs) or a combination of these two cell types for the treatment of ischemic cardiomyopathy (IC) in a Wistar rat model. IC was induced by left coronary artery ligation, and baseline echocardiography was performed seven days later. Animals with a left ventricular ejection fraction (LVEF) of ≤40% were selected for the study. On the ninth day after IC was induced, the animals were randomized into the following experimental groups: UCSCs, UCBECs, UCSCs plus UCBECs, or vehicle (control). Thirty days after treatment, an echocardiographic analysis was performed, followed by euthanasia. The animals in all of the cell therapy groups, regardless of the cell type transplanted, had less collagen deposition in their heart tissue and demonstrated a significant improvement in myocardial function after IC. Furthermore, there was a trend of increasing numbers of blood vessels in the infarcted area. The median value of LVEF increased by 7.19% to 11.77%, whereas the control group decreased by 0.24%. These results suggest that UCSCs and UCBECs are promising cells for cellular cardiomyoplasty and can be an effective therapy for improving cardiac function following IC.